Insulator shield



April 24, 1951 w. L. MEIER 2,550,367

INSULATOR SHIELD Filed April 21, 1950 IN VEN TOR.

Patented Apr. 24, 1951 UNITED STATES PATENT OFFICE This invention relates to insulator shields, and more particularly relates to shields for absorbing penetrating radiation such as gamma or X-rays to protect insulators which are required to retain their insulating qualities after being subjected to penetrating radiation.

As used throughout the specification and claims, the term penetrating radiation refers to alpha, beta, and gamma rays, also to all wave lengths of X-rays and to neutron radiation. The term moderator refers to a substance whose molecules contain a considerable percentage of hydrogen atoms. Examples are water, parafiine, and other light hydrocarbon substances.

Shields for protecting photographic plates are old in the art, as are a large variety of shields designed to be worn by operators of X-ray apparatus to protect them from X-ray burns. So far as is known, no shielding of insulators has been devised because there has been little or no need for such precaution. Recently, with the widespread use of certain plastics for insulators and the necessity of working in the. presence of penetrating radiation, it has been found that precautions must be taken to insure the continued high resistance of such insulators.

When unprotected insulators in measuring instruments are used in the presence of strong penetrating radiation, the insulation resistance is lowered to a value which may render the instrument reading faulty. If the radiation is not too intense, the insulation resistance will increase after the radiation has been removed, and in several hours will return to its original value so that no permanent injury has been eifected. Intense radiation, however, changes this resistance value permanently and even discolors some varieties of plastic insulators. For these reasons adequate shielding must be employed to insure correct readings at all times.

One of the objects of this invention is to provide adequate shielding for insulators to protect them from the eifects of penetrating radiation.

Another object of the invention is to insure maximum and constant insulation resistance at all times.

Another object of the invention is to protect electrical insulators from any and all efiects of penetrating radiation.

Another object of the invention is to provide an inexpensive shield which can be conveniently installed around any rod type insulator.

The invention comprises an insulator shield which includes a first shield of heavy metal surrounding one portion of the insulator. A second shield of similar metal surrounds another portion of the insulator. The two shields overlap one another but do not touch.

For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description taken in connection with the accompanying drawings.

Fig. 1 is a cross sectional view of one type of insulator shield.

Fig. 2 is a cross sectional view of the shield shown in Fig. 1 taken along line 2-2 of that figure.

Fig. 3 is a cross sectional view of another type of shield designed to protect an insulator from neutron radiation.

Fip. 4 is a cross sectional view of the shield of Fig. 3 taken along line 44 of that figure.

Fig. 5 is a cross sectional view of a shield which is similar to the shield shown in Fig. 1, but has a different arrangement of parts.

Fig. 6 is a. partial cros sectional view of a shield similar to that shown in Fig. 3 but having a shell made of insulating material and containing a filling of a heavy metal.

Referring now to Figs. 1 and 2, a base member I0 supports a first shield II. A cylindrical insulator I2 is secured to the shield at its lower end and supports a second shield I3 at its upper end. Both shields are cylindrical in form and enclose and protect theinsulator. The shields overlap each other but do not touch. The insulator may be made of any of the insulating materials commonly used in measuring instruments.

A conducting plate I 4 is shown above the upper shield I3 which may be one of the high voltage conductors in electrostatic voltmeter or one of the stator inductor sectors in a high voltage induction generator.

It will be obvious that X-rays or any other type of penetrating radiation must traverse at least one thickness of the shield material before the insulator can be reached. Constructing the shields of lead is the most efficient manner of cutting down all penetrating radiation (except neutrons), and in this case shields made of iron will give the protection required.

The assembly shown in Figs. 3 and 4 is designed for neutron radiation and comprises a first shell I5 secured to a base III. For neutron shielding the shell is made of cadmium or other similar light material. Inside the shell I5 a quantity of parafiine I6 is placed to act as moderator to slow down the neutrons so they may be inter- 3 cepted by the cadmium barrier adjacent to the insulator l2.

The insulator I2 is secured to the first shell if) at one end and to a second shell I! at its other ends. The second shell is similar in form to the first and also contains a filling or paraffine l8. As in the first arrangement of Figs. 1 and 2, the shells overlap their edges but do not touch. An insulated plate or conductor 20 is secured to the second shell and may be. part of a measuring instrument or other equipment where good insulation is a requirement.

The design shown in Fig. 6 can be used to shield insulators from X-rays by filling the shells l5 and H with lead. The two shells are made of insulating material such as Bakelite; Lucite, etc. Such an insulator shield is opaque to-penetrating radiation and at the same time offers protection from a short circuit which may be" caused by conductive material accidently placed in contact-with both shields;

The assembly shown in Fig. 5 is similar to Fig. 1 except that the upper shield I3 is made with a short cylindrical portion to reduce the capacity of the elements connected to the high voltage supply. The lower shield H protects the greater portion of the insulator l2. In this illustration the corners of the shields are carefully rounded so as to present no sharp points or corners where a high voltage discharge might start.

From the above description it will be evident that the invention provides shielding to protect high voltage insulators from all types of penetrating radiation.

While there has been described and illustrated specific embodiments of the invention, it will be obvious that various changes and modifications may be made therein without departing from the field of the invention which should be limited only by the scope of the appended claims.

I claim:

1. An insulation system for protecting electrical insulators from the effects of X-rays, alpha, beta, and garnina'rays comprising, a cylindrical insulator, a first cylindrical shield made of a material opaque to said rays and mounted so as to enclose and protect the upper portion of the insulator, a second cylindrical shield also made of a material opaque to said rays and mounted so as to enclose and protect the lower portion of the insulator, both of said shields arranged in mutual overlapping manner without touching.

2; An insulation system for protecting electrical insulators from the effects of X-rays comprising, a cylindrical insulator, a first shield made of lead and mounted so as to enclose and protect the upper portion of the insulator, a second shield also made of lead and mounted so as to 4 enclose and protect the lower portion of the insulator, both of said shields arranged in mutual overlapping manner without touching.

3. An insulation system for protecting electrical insulators from the effects of neutron radiation comprising, a cylindrical insulator, a first shield made of cadmium and a moderator and mounted so as to enclose and protect the upper portion of the insulator, a second shield also made of cadmium and a moderator and mounted so as to enclose and protect the lower'portion of the insulator, both of said shields arranged in mutual overlapping manner without touching.

4. An insulation system for protecting electrical insulators from the effects of neutron radiation comprising, a cylindrical insulator, two

shieldsmade of cadmium shells formed to receive and retain paraffine to act as moderators, one of said shields mounted so as to enclose and protect the upper portion of the insulator, the second of said shields-mountedso. as to enclose/and protect thelower portion ofthe insulator, both of said shields-arranged in mutual overlapping manner without touching.

5. An insulation system for'protecting electrical insulators from the. effects of radiation which includes X-rays, alpha, beta, and gamma rays, comprising; a cylindrical insulator and two shields made in theform of retaining shells to receive and retain a material which is opaque to said rays; one of said shields mounted so as to enclose and protect theupper. portion of the insulator, the second of said shields mounted so as to enclose and protect. the lower portion of the insulator, both of said shields arranged in mutual overlappingmanner without touching,

6. An insulation system for protecting electrical insulators from the effects of X-rays, alpha, beta, and gamma rays comprising, a cylindrical insulator, two shields ofv insulating material made in the form of retaining shells to receive and retain a material'which is opaque to said rays, one of said shields-mounted so as to enclose and'protect the upper portion of the. insulator, the second-of said shields mountedso as to enclose and protect the lower portion of the insulator, both of said shields arranged in mutual overlapping manner without touching.v

WILBER L. MEIER.

REFERENCES GITED UNITED STATES PATENTS.

Name Date Williams Oct. 24, 1893 Number 

